Rotary mowers equipped with a double-sail blade, that rotates in a downward cut-out cover, are known as lawnmowers. The blade is driven either electrically or by means of an internal-combustion engine. The known lawnmowers are propelled either on rollers or are designed as so-called air-cushion mowers.
In the case of conventional lawnmowers, the lateral wall of the cover shielding the rotating blade is provided with an ejection hole for the clippings, which hole ends in a collecting bag to catch the clippings ejected by the blade. Blades are known in the art, that are provided in the area of their sail extremities with deflector elements for the ejection of the clippings, which elements protrude above the blade's plane of rotation and, with the rotation of the blade, carry with them the clippings and eject them through the ejection hole of the cup-shaped cover.
The rotary mower disclosed in DE 4,034,978, is equipped with a double-sail blade rotating inside a housing, the walls of which form a cylinder that completely encloses the blade's rotating orbit. At least in the area of the sail extremities, the blade is provided in its direction of rotation at its rear longitudinal edges with deflector elements, that protrude upwards beyond of the blade's plane at one of the sail extremities and downwards at the other sail extremity. The inverse design of the deflector elements at both sail extremities results in that the clippings are ejected upwards by one of the deflector elements and downwards by the other. This process reduces the size of the clippings to such an extent that they can be used as natural fertilizer. In a preferred specific embodiment, the blade sails are provided with U-shaped sections formed from the blade's plane of rotation, along which run the cutting edges of the blade. Practice has shown, however, that especially in the case of longer and damp material to be cut, it was not always possible to obtain a sufficient pulverization of the clippings.
EP 0 300 642 describes a blade for a rotary mower with two sails, on which the front longitudinal edges are provided in their direction of rotation with cutting edges. Each of the cutting edges of the known blade is contoured in the direction of rotation by forming an outer cutting edge section located below the plane of the hub portion, to which section is attached a cutting edge section located on the plane of the hub portion. The sail extremities of the known blade are shaped as upwards slanted guide surfaces opposite the blade's plane of rotation. However, the outer edge areas of the sail extremities are not slanted upwards in order to maintain the lowest possible generating of noise.
The object of the invention is to devise a knife blade for a rotary mower that, even with longer and wet material to be cut, renders satisfactory mowing results and almost pulverizes the clippings. Another object of the invention is to devise a rotary mower with an improved mowing performance, that almost pulverizes the clippings. Still another object of the invention is to devise a retrofit kit by means of which a conventional rotary mower, that presents a cover with an ejection hole on one of its sides, can be retrofitted, so that it ejects in a downward direction the almost pulverized clippings.